Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

BDS2 CDS Prosthodontics Removable > retention > Flashcards

retention Flashcards

1
Q

retention

A

A term used to describe the RESISTANCE of a denture to LIFTING AWAY from the tissues (VERTICAL DISLODGING FORCES).

  • Prevents from being displaced (falling out upper, sticky food dislodging lower)
  • Denture lifting away from tissue

“Any portion of the prosthesis that contacts the teeth and helps to prevent removal of the prosthesis.” (Kratochvil )

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

3 ways to achieve retention

A

mechanical

muscular forces

physical forces

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

mechanical means of achieving retention

A

clasps

  • Engage tooth undercuts (below bulbous part of a tooth
  • Clasps, guide surfaces, precision attachments (used in conjunction with crowns)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

muscular forces means of achieving retention

A

shape of the denture

  • The action of the surrounding musculature on the shape of the non-impression surface (polished surface) of the denture.
  • E.g. tongue, lips, cheek

Patient’s muscular control.
- Work in concert to help retain the denture

Through time when wearers are used to the denture. Clasps wear with time but muscular forces will start to work. If denture is made correctly (too bulky in lingual = tongue will dislodge)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

physical forces means of achieving retention

A

coverage of mucosa

Using existing forces of adhesion, cohesion, surface tension and atmospheric pressure on the impression surface of the denture.

Closeness of adaptation, extent (area covered) of the denture base, peripheral seal.

Negative pressure and peripheral seal to keep denture in place via suction

Not so much Co Cr as heavier and more skeletal - less forces

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

adhesion

A

surface forces of saliva on denture and mucosa

physical force of retention

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

cohesion

A

forces within saliva, viscosity to denture base

physical force of retention

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

atmospheric pressure

A

resistance to displacing forces

physical force of retention

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

2 classifications of retention

A

direct

indirect

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

direct retention

A

resistance to vertical displacement of denture

Clasps, physical forces on oral musculature

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

indirect retention

A

resistance to rotational displacement of the denture

  • Incorporated in the denture
  • help prevent the denture rotating out during function
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

guide planes

A

direct retention
- supplementary retention, close to the base and parallel to the path of insertion

good because frictional retention

  • No deform over loading, insertion and removal
  • Keep the space - no teeth drift

can manufacture if carrying out a restoration e.g. crown made parallel extra orally

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

how to get direct retention

A

close to the base, adjacent to the abutment teeth

similar to support
- Interproximal would be great
- But denture material is rigid
Need to utilise undercuts - alter path of insertion

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

problem with clasps

A

deform over time and wear

also hard to shape the teeth for them

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

principal method of providing mechanical retention

A

clasps

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

clasp

A

metal arm that, when in position contacts the tooth preventing removal of the denture base.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

clasp placement to be effective as a retainer

A

placed below the bulbous part of the tooth (undercut).

  • Engages into undercut
  • Depth is determined by length of clasp

The bulbous portion of the tooth requires identification.
- To accomplish this a SURVEY of the cast is performed.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

materials used for clasps

A

wrought metal and incorporated into the denture base or be included as part of a cast denture base.

19
Q

2 types of occlusal clasp design

A

3 surfaces of tooth
bulk next to saddle, retentive component adjacent to the saddle
- good but longer 15mm so maybe more flexible and easily distorted.

OR
terminates at distal,
2 arms one doesn’t engage in undercut and is not retentive - reciprocal arm.

20
Q

what should clasps be in conjunction with?

A

a rest (supporting component)

Not necessarily to help in occlusal loading
- But prevent clasp slipping down the tooth and damaging gingival margin

21
Q

2 ways clasps can approach the surface

A

occlusally approaching
- terminate in undercut

gingivally approaching
- crossing the gingival margin, from sulcus area up onto the tooth

22
Q

gingivally approaching clasps

A

anterior/premolar/canine mostly below lip line, below sulcus

  • more aesthetic
  • guarantee 15mm in length needed for retention

Terminates determined by undercut

Cross gingival margin
- creates a bridge for infection at gingival crevice - bacteria enter and gather and infection

23
Q

occlusally approaching clasps

A

less subtle,

- tend to be used on molars so less obvious

24
Q

reciprocation

A

As part of the clasp assembly each clasp unit will have an opposing element to the retentive clasp arm to prevent pressure form the clasp acting on the tooth.

Clasps can cause tooth to move when load applied

  • Reciprocal arm helps maintain tooth position
  • Opposite side from the clasp
25
Q

key part of reciprocal arm design

A

When clasp starts to deform the reciprocal arm needs to be in contact -

Always factor in at design - don’t forget to add when adding clasp

26
Q

why would you alter the path of insertion and removal?

A

utilise undercuts to change amount of acrylic needed to not impact on aesthetics

may gain anterior retention with no clasps (desired)

When gain somewhere will lose elsewhere - anterior posterior relationship
- Consider all consequences of altered path

27
Q

what is the ideal pattern of retention?

A

3 clasps

1 will help resist the longitudinal plane of the other 2

Angular pattern of retention
- Biggest triangle possible - more stable (think of 3-legged stool)

28
Q

when would the angular pattern of retention not be possible?

A

bilateral free end saddle

straight line pattern of retention

29
Q

anterior undercuts retention is

A

acrylic not clasps

30
Q

why should you try and simply/minimise denture design where possible?

A

anything added to patient mouth is a plaque trap

every component must therefore have a function

31
Q

how to prevent axial torque on abutment teeth

A

only pressure when denture is loaded (chewing) should be on rests

  • facilitates denture retention
  • prevents axial torque
32
Q

Stress Relieving Clasp System (RPI)

A

used in free-end saddle designs to prevent stress on the last abutment tooth.

made of

  • Mesial Rest
  • Proximal guide plate
  • Gingivally approaching I-bar clasp
33
Q

3 components of RPI system

A
  • Mesial Rest
  • Proximal guide plate
  • Gingivally approaching I-bar clasp
34
Q

rest component of Stress Relieving Clasp System (RP)

A
  • occlusal mesial rest on the tooth

- rounded on the impression surface

35
Q

proximal plate component of Stress Relieving Clasp System (RP)

A
  • adjacent to the saddle
  • guide surface of 2-3mm
  • undercut to permit movement
36
Q

I-bar clasp component of Stress Relieving Clasp System (RP)

A
  • gingivally approaching

- greatest prominence of the tooth contour

37
Q

why do maxillary dentures have less need for RPI?

A

movement restricted by upper hard palate

38
Q

indirect retention

A

resistance to rotational displacement of denture

obtained by the extension of a partial denture base to provide the fulcrum of a class II lever.  
- support leg
39
Q

how to gain more indirect retention?

A

Moving support element away from the saddle area =
More retention

Introduce cingulum rests on canines - become supporting legs/pivot points as further away than mesial of last abutment teeth, so more retention

40
Q

weak indirect retention can occur when

A

Clasp axis and most anterior supporting element (mesial rest) are close together = dislodge easily (poor indirect retention)

41
Q

indirect retainers (5)

A
  • Major connectors
  • Minor connectors
  • Rest
  • Saddle
  • Denture base

principally supporting components
- rests not clasps

42
Q

minimum number of clasps for a denture

A

One clasp on each side of the arch (2 total) should be sufficient depending on the saddle length

43
Q

when is indirect retention key?

A

Indirect retention prevents rotation and can be used to provide stability particularly for free-end saddles or very long bounded saddles

44
Q

when are stress relieving claps system (RPI) predominately used?

A

mandibular free-end saddle case, but can be utilised in the maxillary arch also.

BDS2 CDS Prosthodontics Removable (10 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions